Vibration-damping device



Feb. 17, 1931. A. c. KELLER ET AL VIBRATION DAMPING DEVICE Filed May 14,1927 WW ATTORNEY mat-En; STATES a modified unit of this invention. y 1Referring particularly to Figs. 1 t o 4; there isshown anelectromagnetic phonograph" recorder or reproducer having anelectromag-Q Patented Feb. 17, 1931 menu 'c'. KELLERAim EDWARD. 1;.woman; or Yo'xm, N." in, nssreivons 'ro narrow or may; rom:

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-"'This.invention relates to--.damping devices and more particularlyto-a device for damping mechanical vibrations, such for example as occurin electro-mechanical translating devices adapted to respond toallfrequencies within theaudible range. v e

The object of. the invention is to provide a unitary damping meanshaving a substantially straight line-response characteristic over a wideband of frequencies regardless of normal temperature changes.

invention, there is provided a structure comprising two relativelymovable flat parallel surfaces-located in a chamber, filledor'substantially filled with a viscous material which is displacedlaterallyofi the flat surfaces in response to reciprocal movementbetween them.

The viscous material is one which iscomchanges and the other materials ofthe .unit

broken away ofan electromagnet system with the device of this inventionapplied thereto;

Fig. 2 is a viewin front elevation. of, the parts shown in Fig. ,1;- lFig. 3. is sectionalview of the parts'illustrated.in*Fig..2;

with the-various elements shown in perspectivegand Fig.5 1s a detailedcross-sectional view of net 10 energized by a winding 11. Secured tothev magnet are pole pieces .12 between which'is mounted an armature 13.The armature is provided with a notch and is pivoted on a lmife edge '1being-held in place by a. spring 15. 1 Attached tothe armature is a"stylus holder A; pair of windings 17ers] 1927. Serial No. 191,517..

( BELT; TELEPHONE mom'romns, 'IN'COBBORAIEEWF-NEW Yemen. 1;, Asonromounted coaxially'with the armature and arranged to be connected toa suitable electrical ,circuitby means of the leads 18. The downward'prdj'eetin 'endof the St 1115 holder '16 isprovidedwit a socket in'w'chf'ismouhtthis'i'n-Yentio'n y means f the shortmet'allie flr'Ql;

; [The damping device comprises a cylindrt In accordance with thefeatures ofthis v I to 'the magnet 10'. In the center of the chaincalchambe'r 22 rig'idly mounted with respect her there ismounted'a"post"member 23,"the face of which is in-close space relationto the flexible metallic", diaphragm 24. This diaphragm closes theopening of the chamber and is -rigid'ly" attached to the =bar=2lv sothat itismoved by vi'brations of the armature l3 and {stylus bar 16."'A's shown in-Fig. 4, washparatively insensitive te normal temperatureed aphonograiph'styliis 19 which engages the record 20. Theo'ppositeiend ofthe' stylus {bar isconnected jtothdamping device of ers25', 26 and 27 anda clamping'r1ng28 are "provided so thatthe' diaphragm24 maybe mounted in the chamber opening in suchla way as to :com letelyseal the chamber; Before the chain er isclosed it is filled with aviscous liquid 29, preferably a mixture of about 75% polymerizedcastor-oil and 25% nitro-benzol, which has a viscosity of the order of 2vdyne-seconds per square centimeter.

The vibrationlof the diaphragm displaces the oil from betweenit and thepostmember'23.

The result is that the diaphragm has a mechanical impedance .to'motionwhich is substantially constantf and a substantially pure H resistanceover a'wide range of frequencies. Fig. 4 is an exploded view of -thedevice ,In order 'to'icom ensate for changes in the viscosity o'fthe oilproduced by changes in 22 is. constructed'of, a material with a'comparati vely ow "linear expansion coefiicient and therlength of'the'post' is made such that the cha ngesin thelength of the gap withtem peratjure. will be such as to compensate withthe1correspondingfchanges in the viscosity Yoffloil, j e

F'gfashows a modification of the damping unitinfwhiclra metallic plate30 is mountedon the i'n'ne'rf surface of the diaphragm so,

that the surfaces formin the gap will always be in substantial parallerelation. For most purposes the arrangement shown in the other gures issatisfactory as the variation from a parallel relation will not besufiicient to materially affect the mechanical impedance characteristic.

In many systems the values of the mass and stiffness are known and fromthe required degree of dam ing the value of resistance reu1red can beetermined. It has been found t at the mechanical resistance which willbe added by the use of the unit of this invention is given by theexpression:

Ba A R 2d E being the bulk modulus of the viscous material and {)beingthe frequency which in the case of a and of frequencies is the upperlimitin frequency. For values of d be ow this va ue a stifiness reactionwill be introduced. 7

Also if the length of the gap is greater than that given by theexpression I m I d f!- p being the density of the viscosity material themass reactance is at the resistance.

What is claimed is: 1. In an electro-mechanical translating deviceresponsive to all. frequencies within the audible range, a vibrationdamping means comprising a container, viscous matter in said container,and a vpair of spaced relatively movable members in said containeradapted in their movement to move the viscous matter laterally betweentheir faces, the container and one of the members being made ofmaterials having such different jcoeilicients of expansion as tocompensate for changes in viscosity of the matter in the container.

- 2. In an electro-mechanical translating device responsive to allfrequencies within the audible range, a vibration damping meanscomprising a container for viscous matter viscous matter in thecontainer, and a pair of relatively movable flat-faced members of leastcomparable to approximately equal areas mounted in spaced relation insaid container, the viscous matter filling the chamber to an extent tocover the opposed faces but with sufficient clearance to provide freelateral movement of the viscous matter between the opposing faces.

3. In an electro-mechanical translating device responsive to allfrequencies within the audible range, a vibration damping meanscomprisin a container, a vibrating diaphragm orming a closure for saidcontainer, a fiat-faced member carried by the diaphragm, a stationarymember in said container having a flat face comparable in area to thearea of the first mentioned flat-faced member and located in opposedspaced relation thereto, and viscous matter in the casing adapted forfree lateral movement across the adjacent fiat faces in response tomovement of the vibrating member to control the character of thevibrating movement.

4:. In an electro-mechanical translating device responsive to allfrequencies within the audible range, a vibration dampin meanscomprising a container, a flat-faced vibrating member in one end of thecontainer, a stationary member in the container having a flat facecomparable in area to the area of the vibrating member and located inopposed spaced relation to the vibrating member, and viscous matter inthe container filling said container to an extent to cover the opposedfaces but with sufiicient clearance to permit free lateral movement ofthe viscous matter between said faces,

vice responsive to all freqeuncies within the audible ran e, a vibrationdamping means having a su stantially constant mechanical impedance and apure resistance over a wide range of frequencies and comprising acontainer opposing relatively reciprocal fiatfaced members inthecontainer, and viscous matter in the container moved laterally of theflat-faced members in their relative movement to produce the desiredimpedance and resistance in the movable parts.

6. In an electro-mechan1cal translating device responsive to allfrequencies within the audible range, a vibration damping meanscomprising a container, a pair of opposing relative movable flat-facedmembers in the container, and viscous matter in the container movedlaterally between the flat-faced members in their relative movement, thearea and separation of the flat-faced members being predetermined and sorelated to a chosen viscosity of the matter that the movable part has asubstantially pure resistance over a range corresponding to useful soundvibrations.

7 In an electro-mechanical translating device responsive to allfrequencies within the audible range, a vibration damping meanscomprising a container, a pair of opposing 5. In an electro-mechanicaltranslating demembers by the reciprocation of one member to produce aresistance equal to Where a is the radius and A the area of thefiat-faced members, (1 the separation of the surfaces and the viscosityof the viscous matter.

9. In an electro-mechanical translating device responsive to allfrequencies Within the audible range, a vibrational damping meanscomprisin a container of material having a relatively low linearexpansion coefiicient, a flexible diaphragm closing one end of thecontainer, a post in the container having one end in close spacedrelation to the diaphragm and having a relatively high linear expansioncoefficient, and viscous material in said con-- tainer moved laterallybetween the adjacent faces of the diaphragm and post in the move ment ofthe diaphragm.

In witness whereof, we hereunto subscribe our names this 12th day ofMay, A. D., 1927.

ARTHUR G. KELLER. EDWARD L. NORTON.

